1. Field of the Invention
The present invention relates to an image forming apparatus using a one-component non-magnetic toner. More particularly, the present invention relates to a layer regulating device and method of a developing roller for uniformly regulating the toner layer on the developing roller.
2. Description of the Related Art
Conventional image forming apparatuses using one-component non-magnetic toner have a blade which is in contact with a developing roller to uniformly maintain the amount of toner layers on the developing roller. The technology for applying the blade has been previously filed by the present applicant in Korean Patent Publication 10-1999-016849 which is incorporated by reference in its entirety. FIG. 1 discloses the technology.
In FIG. 1, a photosensitive drum 1 is installed in a housing 2 having a prescribed shape. The surface of the photosensitive drum 1 is charged at a certain potential by a charging roller 3. The charged surface of the photosensitive drum 1 is partly exposed by an exposure unit 4, and accordingly, an electrostatic latent image is formed. The toner supplied through a developing roller 6 is transferred to the electrostatic latent image area, thereby developing the toner image. In order to supply the toner to the developing roller 6, the toner is accommodated in a predetermined space in the housing 2, and an agitator 9 in the toner receptacle 10 agitates the toner while moving. A toner supply roller 8 that rotates in contact with the developing roller 6 supplies the toner to developing roller 6 while being rotated in the same direction as the developing roller 6. In order to regulate the toner layer that attaches to the surface of the developing roller 6, a regulating blade 7 is installed in contact with the developing roller 6.
The regulating blade 7 comprises a metal plate having a predetermined thickness and an elastic force, and generates a contact pressure on the developing roller 6. The contact pressure via the elastic force allows the toner passing through between the blade 7 and the developing roller 6 to be charged with friction, thereby charging the toner at a certain polarity.
The toner layer formed by the developing roller 6 is determined by the height H from a contacting point between the developing roller 6 and the blade 7 to a free end of the blade 7 and the bending angle θ of the free end. In other words, the toner that is continuously supplied between the developing roller 6 and the blade 7 by the toner supply roller 8 impacts on a bending portion 7a and remains there for a predetermined time, thereby generating frictional charging. And, a part of the toner aggregated by the bending potion 7a overcomes the elastic force and passes through between the developing roller 6 and the blade 7, thereby forming a certain toner layer.
As shown in FIG. 2, to prevent the toner from spilling between both ends of the blade 7 and the inner wall of the housing 2, a sealing member 11 is connected to both ends of the blade 7. Accordingly, a large amount of toner substantially remains in a particular area formed by the bending portion 7a and both sealing members 11 for a long period of time, thereby generating frictional charging.
However, the image area where the toner is substantially developed in the photosensitive drum 1 begins from a portion inward by a certain distance from both ends of the photosensitive drum 1. Therefore, a large amount of toner is substantially consumed only in a section A of the developing roller 6, which corresponds to the image area of the photosensitive drum 1. The toner remains in both ends of the bending portion 7a except for section A for a long period of time.
The toner is continuously subjected to stress without being touched by the blade 7 due to the height H of the bending portion 7a. More specifically, the toner consists of resin material and an additive added to the surface of the resin material, and the additive may be drawn into the resin material, or a stress phenomenon in which the additive is separated from the resin material may occur. In addition, due to the frictional force, the toner melts and adheres to the contacting portion of the developing roller 6 and the blade 7. Therefore, the so-called fixed toner layer in the form of a belt that becomes gradually thick is formed. In this case, the blade 7 is raised by the fixed toner layer from the surface of the developing roller 6. As a result, too much of the toner is supplied between the developing roller 6 and the blade 7 and degrades the quality of the image.